This invention relates to the magnetic navigation of medical devices, and in particular to magnetic medical devices with changeable magnetic moments, and to methods of navigating magnetic medical devices with changeable magnetic moments.
It has long been proposed to magnetically navigate catheters through the body with an externally applied magnetic field. Recent advances have made the magnetic navigation of catheters and other medical devices practical. Typically, the medical device is provided with a permanent or a permeable magnetic element. An external source magnet, which may be a permanent magnet, an electromagnet, or a superconducting electromagnet, is used to apply a magnetic field and/or gradient to an operating region inside a patient to act on the magnetic element in the medical device to orient and/or move the medical device in the operating region. The medical device is oriented and/or moved by changing the magnetic field and/or gradient applied by the external source magnet.
In the case of stationary electromagnetic and superconducting electromagnetic source magnets, changing the magnetic field and/or gradient is accomplished by changing the currents supplied to the source magnet. In the case of moveable source magnets, changing the magnetic field and/or gradient is accomplished by changing the position and/or orientation of the source magnet. If the moveable source magnet is an electromagnet or a superconducting electromagnet, the magnetic field and/or gradient can also be changed by changing the current supplied to the magnet.
While systems with stationary electromagnets and superconducting electromagnets provide fast, safe, and effective navigation of medical devices, it can be expensive to construct and maintain a system that operates in real time to provide unrestricted navigation in the body. Similarly while systems with moving source magnets provide fast, safe, and effective navigation of medical devices, it can be expensive to construct and maintain a system that can accurately move the source magnets to make a selected change in the magnet field and/or gradient.
The changing fields and gradients created by the source magnets are strong and will usually require shielding at many health care facilities. This shielding is another difficulty and expense of magnetic navigation systems that employ changing source magnetic fields and gradients to navigate magnetic medical devices in the body.
While systems using changing source magnet magnetic fields and gradients provide precise control and a high degree of navigational flexibility, for some types of medical procedures a less complicated, less expensive, and preferably more compact navigation system would be desirable.